Maker



(NoMoael.)

E. T. SGHOONMAKER.

ELECTRIC WIRE INSULATOR.

Patented July '7,- 1885.

Unire@ Farnnr Ormea.

EDV/'ARD T. SOHOONMAKER, OF NEW YORK, N. Y., ASSIGNOR OF ONE-HALF TOJOHN E. SMITH, OF SAME PLACE.

ELECTREC-WlRE INSULATOR.

SPECIFICATION forming part of Letters Patent No. 321,646, d? ed July '7,1885.

Application liled December 11, 18H4. (No model.)

To all whom t may concern:

Beit known that I, EDWARD T. Sor-loon- Maxnrz, of the city and county ofNew York, in the State of New York, have invented a new and usefulImprovement in Electric Insulators, of which the following is aspecilication, reference being had to the accompanying drawings.

This invention relates to insulators for electric conductors, especiallyto the insulators ot'- aerial telegraphic and telephonie circuits. Itsobject is to prevent or reduce the leakage of the electric current overtheinsulators during wet weather. Heretot'ore the shank of suchinsulators has generally been cemented or screwed into the glass shieldfor a distance of an inch and a halt or twoinches, thus making tive orsix square inches of contact between the two. In some other forms ofinsulator the shield is held on the shank by a single pin or armentering a groove; but in these also a large portion of the body of theshank touches the inner surface of the shield. So large a contactbetween shank and shield, when both become damp in rainy or foggyweather, allows enough of the electric current to leave the line toseriously interfere with its operation.

The object of my invention is to diminish the surface-connection betweentheshank and the shield; and to this end my invention consists,essentially, in the combination, in an insulator7 of a shield having agroove or grooves in its inner surface and a shank with spurs whichenter the said groove or grooves and so support and hold the shield thatit has no contact whatever with the body of the shank.

In carrying out my invention, the shank and the shield may be of anymaterial or materials of sufticient strength, provided one of them is agood non-conductor; but it will probably be most advantageous to makethe shank of iron and the shield of glass, as in the insulators now incommon use.

In the accompanying drawings, Figure l is an elevation of an insulatorconstructed according to my invention, the shield being shown insection. Fig. 2 is a horizontal section in the linear of Fig. 1. Fig. 3is an elevation, with the shield iu section, of an insn- 5o latordiffering in its details from that shown in Figs. l and 2, butillustrating my inven tion. Fig. 4 is a horizontal section on the line xof Fig. 3. Fig. 5 is a central vertical section of the shield shown inFigs. 8 and 4.

Similar letters ot' reference indicate corresponding parts in theseveral figures.

A is the shank, and B is the shield. The shank may have that end, a,which is to be fastened to the cross-arm or pole of any known 6o orsuitable form. I have represented it of a round form suitable to bedriven into a hole in a cross-arm. The shield may have any desired formexternally. The body ofthe shank or that portion of it which enters theshield is considerably smaller than the bore of the shield, and isconstructed or provided with radiating spurs c c, of which l prefer thatthere should not be less than three.

In the example of my invention shown in 7o Figs. l and 2 the spurs c care arranged spirally, so that they practically form parts of the threadof a male screw; and in this example the shield has the groove b in itsinterior or bore in the form of a female screwthread, the bore andscrew-thread tapering toward the crown, and being of such size relativeto the circle circumscribing the points or extremities of the spurs c cthat when the shield is screwed onto the said spurs it will 8o becometight and rigid thereon, without the body ofthe shank touching eitherthe side or the crown of the shield.

In the example shown in Figs. 3, 4, and 5, instead of a single groove inthe form of a male screw-thread, there are in the interior o1` theshield several grooves, d d, corresponding in number with the spurs onthe shank, each in the form of an inverted "i, one portion beingvertical or parallel with the axis of the go shield and the otherportion being horizontal or ruiming in a direction circumferential tothe shield. rlhese grooves are open at the bottom or toward the mouth ofthe shield, terminating in a portion of the shield which is wider thanthe portion in which they are formed. The shield being placed directlyon the shank with the grooves opposite the spurs,

and then turned a short distance to bring the lorizontal orcircumferential portions of the grooves el d on the spurs, the latteralone will touch the shield and prevent the line-wire or conductor frompulling it otl from the shank. ln all eases I prefer to make the angleof the transverse section oi' the groove or grooves inore obtuse thanthe Corresponding angle or" the extremities ofthe spurs, as shown inFigs. l and 3, so that only the points ot' the latter will touch theshield, leaving;` the body entirely free freni Contact therewith. Thegroove e to receive the line wire or conductor should, preferably, beopposite or nearly opposite the spurs ofthe shank, to preventunnecessary strain on said spurs.

By this invention, while l ain enabled to se curely fasten the shield toits support, l. ani

enabled t-o reduce thc contact between thtin to about one sixty-fourthpart ot' a square inch, or about one three-hundredth part o1" itc usualamount, and not only this, but the Contact being higher up in the shieldis less liable to beconie wet and the distance which the current inusttravel over the inner surl'acc of the shield is greatly increased.

That I elaiin as nry invention, and desire to secure by Letters Patent,is*

l. The combination, in au insulator', ot' a shield having a grooredinner surface and a shank having spurs on dii't'erent sides thereof' toengage with the said grooved suri'ace, and

support and hold the shield out ol' contact with the body ot' the shank,substantially as herein described.

2. The combination of the shield having in its interior a groove in theforni of a female screw-thread and the shank having a series of spursarranged at distances apart thereon,

on diii'erent sides thereof', and in spiral relat tion to each other tot'orni portions ot' a inale screwthread corresponding with the groove orteniale thread in the shield, substantially as herein described.

The combination ofthe shank havingr at enc end ot' its exterior a seriesoi' spurs arranged to forni sections ot' a screwthread and the shieldhaving in its interior a taper t'eniale screw-thread fitting the saidspurs to become tight thereon, while the end ofthe shank docs u

